Notepad++ supports syntax highlighting and code folding for over 50 programming, scripting, and markup languages.[7][9] It attempts to automatically detect the language that a given file uses, using a modifiable list of file extension bindings. Users may also manually set the current language, overriding the extension's default language. The program also supports autocompletion for a subset of the API of some programming languages.

The following languages are natively supported by Notepad++ as of version 6.6:

Users can also define their own language (for syntax highlighting) and its respective API (for autocompletion) by using the built-in User Language Define System.[7] Users may configure the syntax highlighting's font styles per element, per language, and the resulting formatted script may be printed in full-color (WYSIWYG). Additionally, Notepad++ displays indent guidelines when source code is indented with tab characters, and highlights closing braces, brackets and tags.

Notepad++ has support for macros and plugins.[10] Currently, there are 27 official plugins for Notepad++, 10 of which are included by default in the program.[11] The first plugin to be included in the program was "TextFX", which includes features such as W3C validation for HTML and CSS, text sorting, character case alteration and quote handling.[12] Plugin site lists over 140 compatible plugins.[citation needed]

This project is originally by Don Ho, a developer based in Paris and graduated from Paris Diderot University in 2000. This project, based on the Scintilla editor component, is written in C++ with only Win32API calls using only the STL in order to increase performance and reduce program size. The aim of Notepad++ is to reduce overall processor usage by using efficient binaries that require fewer CPU computations.[7]

Notepad++ supports switching into local language after providing a single XML file containing all text that should be translated. As of 2013, the user community has contributed translations into many languages, as well as into some local dialects.

If F1 is pressed or the About dialog is opened while the currently selected text contains a name, a new document is created and a quote from that person is entered using simulated typing.[13] Among the names that trigger this easter egg are Bill Gates, Linus Torvalds, Brian Kernighan and Darth Vader. Selecting the text 'random' selects a random quote.[14]

Notepad++ has been criticized for having sexist jokes as Easter eggs. It has also been criticized for having jokes of bad taste. The jokes were discovered in a forum on late 2012.[15] In April 2013, a user of SourceForge.net opposed them in a discussion.[16] In a reply to the opposition, Don Ho, calling them as one of the features of Notepad++, said that they would be kept.[17] However, other discussions in SourceForge.net[18] and Reddit.com[19][20] were made in this regard in June 2014. After then, Don Ho officially replied that all the sexist jokes would be removed from the next release and such jokes would never be in Notepad++ binary.[21] Since then, a few jokes have been removed from Notepad++.[22]

In March 2008, the "Boycott Beijing 2008" banner was placed on Notepad++'s SourceForge.net homepage.[23] A few months later, most users in China were unable to reach the SourceForge.net website for about a month (June 26, 2008 – July 24, 2008). This led to the widespread belief that China had banned SourceForge.net in retaliation for the Boycott banner.[24][25][26]

In January 2010, the US government forced open source project hosts to comply with US law and deny access from five countries (Cuba, Iran, North Korea, Sudan, and Syria). As a response to what the developer felt was a violation of the free and open-source software (FOSS) philosophy, in June 2010, Notepad++ moved out of US territorial jurisdiction by releasing a version on TuxFamily, in France.[27][28]

On 12 January 2015, the Notepad++ website was hacked in response to Notepad++ version 6.7.4 being titled the "Je suis Charlie edition".[30] The words "There is no god but God, Muhammad is the messenger of God" were displayed across the top of the page along with a song praising Muhammed. The hacked webpage displayed arguments against the USA for killing people in Iraq and Afghanistan. The hackers claimed to be the FallaGa Team as part of the Tunisian Cyber Resistance.[31]